A touch panel is known as a device provided on a display surface of various display apparatuses, such as a liquid crystal display and a cathode ray tube (CRT), and enables input of information by touching the screen. Typical forms of touch panels include a resistive touch panel having two electrode substrates which are arranged so that the conductive layer provided on each substrate is faced with each other.
Conventional electrode substrates for resistive touch panels include a substrate made of a glass plate, a resin plate or a thermoplastic polymer film, and a conductive layer formed on the substrate. The conductive layer contains a conductive metal oxide such as indium tin oxide (ITO) and zinc oxide.
In conventional electrode substrates, transmittance of visible light having a relatively short wavelength is decreased due to reflection and absorption on the conductive layer. The total transmittance is therefore decreased and the light transmitted through the touch panel becomes yellow or brown, making it difficult to show accurate color of the display device on the touch panel.
In order to solve the problem, Japanese Patent Laid-Open Publication No. 6-218864 as the first prior art proposes a laminate in which a high refractive index layer having a refractive index higher than that of both the conductive layer and the substrate is formed between the conductive layer and the substrate, and a laminate in which a low refractive index layer having a refractive index lower than that of both the conductive layer and the substrate is formed between the conductive layer and the substrate. According to the first prior art laminates, the reflectance at a wavelength around 550 nm is decreased as shown in FIG. 5, while the transmittance at a wavelength around 550 nm is improved as shown in FIG. 6. Consequently, the total transmittance is improved. However, the problem of coloring of transmitted light to yellow or brown has not been solved.
Japanese Patent Laid-Open Publication No. 11-286066 as the second prior art proposes a conductive film in which a multilayer optical film is laminated between the conductive layer and the substrate.
The second prior art conductive film, however, has complicated structure and is high in production cost because it has a number of optical films.